Cellular radio communication system

Abstract

A cellular radio communication system operating in accordance with a time division multiple access protocol assigns different fractional loading factors to different time slots. As a result, as well as because of the effects of local propagation conditions, different time slots will have different interference levels. A mobile station in a worst-case propagation environment (such as near the edge of a cell or when subject to severe shadowing fading) can be assigned a time slot having a low interference level, while a mobile station in a good propagation environment can be assigned a time slot having a higher interference level.

1. A cellular radio communication system, comprising:
 a primary station; and 
 a plurality of secondary stations,
 wherein the system operates according to a time division multiple access protocol in which transmissions between said primary station and said secondary stations take place in time slots within transmission frames, 
 wherein different time slots have different fractional loading factors; and 
 wherein a call is assigned to a first time slot having a worst carrier to interference ratio that enables a quality of service required for the call to be provided. 
 
 
     
     
       2. The cellular radio communication system of  claim 1 , wherein the system operates according to a code division multiple access protocol and in that the different fractional loading factors are implemented by assigning different numbers of spreading codes to different time slots. 
     
     
       3. A primary station for use in a cellular radio communication system, said primary station comprising:
 means for operating according to a time division multiple access protocol in which transmissions between said primary station and a plurality of secondary stations take place in time slots within transmission frames; 
 means for applying different fractional loading factors to different time slots; and 
 means for determining an interference level in different time slots and for assigning a call to a first time slot having a worst carrier to interference ratio that enables a quality of service required for the call to be provided. 
 
     
     
       4. The primary station of  claim 3 ,
 wherein the system operates according to a code division multiple access protocol; and 
 wherein said primary station further comprises means for assigning different numbers of spreading codes to different time slots. 
 
     
     
       5. A secondary station for use in a cellular radio communication system, said secondary station comprising:
 means for operating according to a time division multiple access protocol in which transmissions between a primary station and said secondary station take place in time slots within transmission frames, wherein different fractional loading factors are applied to different time slots; and 
 means for determining the interference level in different time slots and for requesting a connection to be assigned to a first time slot having a worst carrier to interference ratio that enables a quality of service required for the call to be provided. 
 
     
     
       6. A method of operating a cellular radio communication system including a primary station and a plurality of secondary stations, the method comprising:
 operating the system according to a time division multiple access protocol in which transmissions between the primary station and the secondary stations take place in time slots within transmission frames; 
 applying different fractional loading factors to different time slots; and 
 assigning a call to a first time slot having a worst carrier to interference ratio that enables a quality of service required for the call to be provided. 
 
     
     
       7. The method of  claim 6 , further comprising:
 operating the system according to a code division multiple access protocol; and 
 assigning different numbers of spreading codes to different time slots.